I'll never forget how the math professors would switch from edition x to edition x+1 with the only clearly visible difference being the homework assignment questions.
I truly hope that this is not just a trove of books, but also a signaling of the change in culture from opportunism at the expense of the students to openness.
I am a free text author (one of mine is an entry on OP's page). If you want change, here is something you can do.
When you are contacted by the alum reps at your school, GaTech or otherwise, don't ask about the football team. Ask if the faculty are rewarded for writing books that are Free.
People respond to rewards. Said less abstractly, I have been told a lot, often by young folks starting out, that they have a good idea but cannot afford to spend the time on a project that would not be recognized at their institution when they come up for tenure or promotion.
(My institution had the foresight to recognized this kind of work, for which I can only say how great that was of them.)
For the most part, professors have to use books that the university bookstore can obtain. Since the publishers were always bumping up the edition, that meant using the new edition. When (and where) I was going to school, most professors would turn a blind eye to students using an old edition. Many would even go as far as supporting students with the old edition. A few would recommend entirely different books if they felt that they were better. I even had one professor who paid students for finding errors in a book that he wrote, even if he knew that the student was using a photocopy of his book.
Very few professors are opportunists and most would prefer an open culture. They are simply stuck with the rules of a system that preys upon students.